1. Technical Field
The present invention relates to a technology for displaying an image.
2. Related Art
Liquid crystal display apparatuses are each provided with a plurality of scanning lines, a plurality of data lines, and a plurality of pixels each corresponding to one of intersections of the scanning lines and the data lines. In general, such a pixel includes a pixel electrode, a common electrode, a liquid crystal element interposed between the pixel electrode and the common electrode, and a transistor which is provided between the pixel electrode and one of the data lines and which is turned on/off in accordance with a scanning signal supplied from one of the scanning lines. In such a liquid crystal display apparatus, in order to prevent the occurrence of image sticking of liquid crystal, an alternate current driving method is employed. In this alternate current driving method, a common electric potential having a constant electric potential level is supplied to a common electrode, and further, the polarity of a data electric potential, which is in accordance with a gray-scale level with which display is to be performed and which is supplied to the pixel electrode, is periodically reversed relative to the common electric potential. In the case where a maximum value of the data electric potential is denoted by Vmax, and the common electric potential is denoted by Vcom, in the alternate current driving method, as shown in FIG. 17A, a selection transistor and a drive circuit which supplies the data lines with corresponding data electric potentials each require a withstand voltage denoted by 2|Vmax−Vcom|.
There is known a method in which, in order to lower a withstand voltage required for the drive circuit, the polarity of the common electric potential Vcom is reversed relative to a reference electric potential as a center of the reverse (for example, refer to JP-A-2002-41003). According to this method, as shown in FIG. 17B, a voltage denoted by |Vmax−Vcom| is sufficient for the withstand voltage of the drive circuit.
Nevertheless, in the technology disclosed in JP-A-2002-41003, the withstand voltage of the transistor results in a voltage denoted by 3|Vmax−Vcom|, as shown in FIG. 17B. It is conceived, therefore, to write an electric potential equal to the common electric potential Vcom into each of all pixels before reversing the polarity of the common electric potential Vcom.
Here, in order to maintain the cycle of the alternate current driving, first, a scanning speed is necessary to be made more than double a current scanning speed. Second, when focusing attention on pieces of data on individual lines being scanned, it is necessary to provide a vertical scanning period in order to perform the writing of an electric potential equal to the common electric potential Vcom into each of all pixels, and this leads to an addition of a period during which pieces of off data are displayed. As a result, brightness is degraded in the case of liquid crystal operating in a normally black mode, and contrast is degraded in the case of liquid crystal operating in a normally white mode. In order to mitigate influences due to these degradations, it is necessary to further shorten each vertical scanning period. Thus, it is necessary to shorten a period of time necessary to perform writing into each of pixels.
For the shortening of a period of time for writing into each of pixels, however, there have been many technical problems, such as lowering of time constant of wirings inside a panel, enhancement of a driving capability of a drive circuit, and shortening of settling time, and thus, the realization thereof has been difficult.